1. Field of the Invention
This invention relates to an electrophotograhic copying apparatus which is capable of copying by an image light entering from the exterior of the copying apparatus provided with a photosensitive member into the interior of the apparatus.
In particular, the present invention relates to an electrophotographic copying apparatus which is capable of copying both from a board surface on which recording can be effected by writing means and an original placed on an original supporting table.
2. Related Background Art
In recent years, along with the advance of the multi-functionalization of an electrophotographic copying apparatus, it has been devised to copy, besides an original placed on an original supporting table, the image information light of a microfilm, a slide film, a board surface or the like obtained outside of the apparatus body, by the electrophotographic copying apparatus body.
For example, there has recently been proposed a method of recording the information written on a board surface by the electrophotographic system. The methods of this type include a method whereby board-written information is directly imaged on the belt-like or drum-like photosensitive member of a conventional electrophotographic copying apparatus and is copied on a transfer material such as plain paper by the conventional electrophotographic process, and a method whereby boardwritten information is once imaged on a field lens provided on an original supporting table, and the formed image is re-imaged on the photosensitive member through an optical system in the electrophotographic copying apparatus and is transferred to a transfer material by the conventional process for copying.
Both of these methods are capable of copying from an original placed on the original supporting table and copying from board-written information onto plain paper and are improved in recording density as compared with the conventional digital system, and when multiple copies are to be obtained, there is no waste of time attributable to the copying speed if the board surface is once copied and then the transfer material obtained by that copying is secondarily copied as an original to be copied.
In electrophotogrpahic copying apparatuses, it has been a widely-employed practice to apply a light to a photosensitive member (hereinafter referred to as blank exposure) with a view to making the portions before and after the image area and the side edges, the leading end, etc. of copying paper into non-image areas to thereby prevent useless consumption of developer or obtain a desired blank portion.
As effective means for such blank exposure, the techniques of providing a shutter member (hereinafter referred to as the blank shutter) and using the light of an original illuminating light source to thereby eliminate the necessity of providing any special light source for blank exposure and achieve the compactness and reduced cost of the apparatus are proposed in U.S. Pat. No. 3,724,942, Japanese Laid-Open Patent Application No. 161258/1980 and Japanese Laid-Open Utility Model Application No. 18251/1983.
However, even in the aforedescribed electrophotogrpahic copying apparatuses capable of copying of the board surface or the like, blank exposure is necessary during the board surface copying mode.
It is conceivable to provide a blank shutter on the board surface side in order to effect blank exposure in the board copying mode, but this results in the bulkiness and higher cost of the apparatus.
In this regard, an apparatus of the movable original table type is conceivable as an image forming apparatus to be used. The apparatus of the movable original table type has a merit that since the imaging optical system in the image forming apparatus is fixed, information written on the board surface should only be imaged at the entrance of the imaging optical system and thus the construction of the board copying apparatus is simple. It is more preferable for the copying paper on which copying has been effected to come out in a direction perpendicular to the board surface because the user can take the copying paper easily and quickly. In such a case, the copying apparatus is disposed so that the direction of movement of the original table is substantially perpendicular to the board surface.
In the copying apparatus of the movable original table type, the original table is moved in the following sequence. First, in order to move the leading end of an original to the opening portion for original exposure, the original table is moved with the trailing end of the original as the head. This is called the back scan of the original table. When the leading end of the original comes to the opening portion for original exposure, exposure is effected from the leading end of the original and the original table is moved with the leading end of the original as the head. This is called the forward scan of the original table. When exposure is effected up to the trailing end of the original, the original table is returned to its initial position (home position) by the back scan.
As described above, in the copying apparatus of the movable original table type, there are a series of movements such as the back scan, forward scan and back scan of the original table and, therefore, if the direction of movement of the original table of the copying apparatus is disposed in a direction intersecting the board surface, the original table may sometimes protrude from the board surface during the back scan or during the forward scan, and this has led to the disadvantage that the original table interferes with or surprises the user who is board-writing or copying the board.
Also, in the above-described example of the prior art, for the formation of the optical path during the board copying mode, it has been necessary to remove a cover such as the pressure plate of the original table and use the apparatus with the glass of the original table maintained uncovered or to increase the movement distance of the original table and make the original table uncovered. It has also been necessary to shield the space between the board scanning apparatus and the copying apparatus from light to thereby prevent the information of the board surface from being disturbed and, moreover, where there is no pressure plate during the original copying mode, remarkable image deterioration has been brought about in the case of an original of light-transmitting material or an original of small size.